Provided by: perl-tk_804.033-1build1_amd64 
NAME
Tk::Font - Create and inspect fonts.
SYNOPSIS
$widget->Font(option?, arg, arg, ...?)
$font->Option?(arg, arg, ...)?
DESCRIPTION
The Font method provides several facilities for dealing with fonts, such as defining named
fonts and inspecting the actual attributes of a font. The command has several different
forms, determined by the first argument. The following forms are currently supported:
$font->actual(-option?)
$widget->fontActual(font?, -option?)
Returns information about the actual attributes that are obtained when font is used on
$font's display; the actual attributes obtained may differ from the attributes
requested due to platform-dependant limitations, such as the availability of font
families and pointsizes. font is a font description; see "FONT DESCRIPTION" below.
If option is specified, returns the value of that attribute; if it is omitted, the
return value is a list of all the attributes and their values. See "FONT OPTIONS"
below for a list of the possible attributes.
$font->configure(-option??=>value, -option=>value, ...?)
Query or modify the desired attributes for $font. If no -option is specified, returns
a list describing all the options and their values for fontname. If a single -option
is specified with no value, then returns the current value of that attribute. If one
or more option-value pairs are specified, then the method modifies the given named
font to have the given values; in this case, all widgets using that font will
redisplay themselves using the new attributes for the font. See "FONT OPTIONS" below
for a list of the possible attributes.
Note: the above behaviour differs in detail to configure on widgets, images etc.
$font = $widget->Font(-option=>value, ...>?)
$font = $widget->fontCreate(?fontname??, -option=>value, ...>?)
Creates a new font object and returns a reference to it. fontname specifies the name
for the font; if it is omitted, then Tk generates a new name of the form fontx, where
x is an integer. There may be any number of option-value pairs, which provide the
desired attributes for the new named font. See "FONT OPTIONS" below for a list of the
possible attributes.
Note: the created font is not shared between widgets of different MainWindows.
$font->delete
$widget->fontDelete(fontname?, fontname, ...?)
Delete the specified named fonts. If there are widgets using the named font, the
named font won't actually be deleted until all the instances are released. Those
widgets will continue to display using the last known values for the named font. If a
deleted named font is subsequently recreated with another call to fontCreate, the
widgets will use the new named font and redisplay themselves using the new attributes
of that font.
$widget->fontFamilies
The return value is a list of the case-insensitive names of all font families that
exist on $widget's display.
$font->measure(text)
$widget->fontMeasure(font, text)
Measures the amount of space the string text would use in the given font when
displayed in $widget. font is a font description; see "FONT DESCRIPTION" below. The
return value is the total width in pixels of text, not including the extra pixels used
by highly exagerrated characters such as cursive ``f''. If the string contains
newlines or tabs, those characters are not expanded or treated specially when
measuring the string.
$font->metrics(-option?)
$widget->fontMetrics(font?, -option?)
Returns information about the metrics (the font-specific data), for font when it is
used on $widget's display. font is a font description; see "FONT DESCRIPTION" below.
If option is specified, returns the value of that metric; if it is omitted, the return
value is a list of all the metrics and their values. See "FONT METRICS" below for a
list of the possible metrics.
$widget->fontNames
The return value is a list of all font objects that are currently defined for
$widget's MainWindow.
FONT DESCRIPTION
The following formats are accepted as a font description anywhere font is specified as an
argument above; these same forms are also permitted when specifying the -font option for
widgets.
[1] fontname
The name of a named font, created using the fontCreate method. When a widget uses a
named font, it is guaranteed that this will never cause an error, as long as the named
font exists, no matter what potentially invalid or meaningless set of attributes the
named font has. If the named font cannot be displayed with exactly the specified
attributes, some other close font will be substituted automatically.
[1a] $font
A font object created using the Font method. This is essentially the same as using a
named font. The object is a reference to the name, and carries additional information
e.g. which MainWindow it relates to in an manner peculiar to perl/Tk.
[2] systemfont
The platform-specific name of a font, interpreted by the graphics server. This also
includes, under X, an XLFD (see [4]) for which a single ``*'' character was used to
elide more than one field in the middle of the name. See "PLATFORM-SPECIFIC ISSUES"
for a list of the system fonts.
[3] [family,?size,??style,??style ...?]
A properly formed list whose first element is the desired font family and whose
optional second element is the desired size. The interpretation of the size attribute
follows the same rules described for -size in "FONT OPTIONS" below. Any additional
optional arguments following the size are font styles. Possible values for the style
arguments are as follows:
normal bold roman italic
underline overstrike
[4] X-font names (XLFD)
A Unix-centric font name of the form
-foundry-family-weight-slant-setwidth-addstyle-pixel-point-resx-resy-spacing-width-charset-encoding.
The ``*'' character may be used to skip individual fields that the user does not care
about. There must be exactly one ``*'' for each field skipped, except that a ``*'' at
the end of the XLFD skips any remaining fields; the shortest valid XLFD is simply
``*'', signifying all fields as defaults. Any fields that were skipped are given
default values. For compatibility, an XLFD always chooses a font of the specified
pixel size (not point size); although this interpretation is not strictly correct, all
existing applications using XLFDs assumed that one ``point'' was in fact one pixel and
would display incorrectly (generally larger) if the correct size font were actually
used.
[5] option value ?option value ...?
A properly formed list of option-value pairs that specify the desired attributes of
the font, in the same format used when defining a named font; see "FONT OPTIONS"
below.
When font description font is used, the system attempts to parse the description according
to each of the above five rules, in the order specified. Cases [1] and [2] must match the
name of an existing named font or of a system font. Cases [3], [4], and [5] are accepted
on all platforms and the closest available font will be used. In some situations it may
not be possible to find any close font (e.g., the font family was a garbage value); in
that case, some system-dependant default font is chosen. If the font description does not
match any of the above patterns, an error is generated.
FONT METRICS
The following options are used by the metrics/fontMetrics method to query font-specific
data determined when the font was created. These properties are for the whole font itself
and not for individual characters drawn in that font. In the following definitions, the
``baseline'' of a font is the horizontal line where the bottom of most letters line up;
certain letters, such as lower-case ``g'' stick below the baseline.
-ascent
The amount in pixels that the tallest letter sticks up above the baseline of the font,
plus any extra blank space added by the designer of the font. ($font->ascent is
provided for compatibility.)
-descent
The largest amount in pixels that any letter sticks down below the baseline of the
font, plus any extra blank space added by the designer of the font. ($font->descent
is provided for compatibility.)
-linespace
Returns how far apart vertically in pixels two lines of text using the same font
should be placed so that none of the characters in one line overlap any of the
characters in the other line. This is generally the sum of the ascent above the
baseline line plus the descent below the baseline.
-fixed
Returns a boolean flag that is ``1'' if this is a fixed-width font, where each normal
character is the the same width as all the other characters, or is ``0'' if this is a
proportionally-spaced font, where individual characters have different widths. The
widths of control characters, tab characters, and other non-printing characters are
not included when calculating this value.
FONT OPTIONS
The following options are supported on all platforms, and are used when constructing a
named font or when specifying a font using style [5] as above:
-family => name
The case-insensitive font family name. Tk guarantees to support the font families
named Courier (a monospaced ``typewriter'' font), Times (a serifed ``newspaper''
font), and Helvetica (a sans-serif ``European'' font). The most closely matching
native font family will automatically be substituted when one of the above font
families is used. The name may also be the name of a native, platform-specific font
family; in that case it will work as desired on one platform but may not display
correctly on other platforms. If the family is unspecified or unrecognized, a
platform-specific default font will be chosen.
-size => size
The desired size of the font. If the size argument is a positive number, it is
interpreted as a size in points. If size is a negative number, its absolute value is
interpreted as a size in pixels. If a font cannot be displayed at the specified size,
a nearby size will be chosen. If size is unspecified or zero, a platform-dependent
default size will be chosen.
The original Tcl/Tk authors believe sizes should normally be specified in points so
the application will remain the same ruler size on the screen, even when changing
screen resolutions or moving scripts across platforms. While this is an admirable goal
it does not work as well in practice as they hoped. The mapping between points and
pixels is set when the application starts, based on alleged properties of the
installed monitor, but it can be overridden by calling the scaling command. However
this can be problematic when system has no way of telling if (say) an 11" or 22"
monitor is attached, also if it can tell then some monitor sizes may result in poorer
quality scaled fonts being used rather than a "tuned" bitmap font. In addition
specifying pixels is useful in certain circumstances such as when a piece of text must
line up with respect to a fixed-size bitmap.
At present the Tcl/Tk scheme is used unchanged, with "point" size being returned by
actual (as an integer), and used internally. Suggestions for work-rounds to
undesirable behaviour welcome.
-weight => weight
The nominal thickness of the characters in the font. The value normal specifies a
normal weight font, while bold specifies a bold font. The closest available weight to
the one specified will be chosen. The default weight is normal.
-slant => slant
The amount the characters in the font are slanted away from the vertical. Valid
values for slant are roman and italic. A roman font is the normal, upright appearance
of a font, while an italic font is one that is tilted some number of degrees from
upright. The closest available slant to the one specified will be chosen. The
default slant is roman.
-underline => boolean
The value is a boolean flag that specifies whether characters in this font should be
underlined. The default value for underline is false.
-overstrike => boolean
The value is a boolean flag that specifies whether a horizontal line should be drawn
through the middle of characters in this font. The default value for overstrike is
false.
PLATFORM-SPECIFIC ISSUES
The following named system fonts are supported:
X Windows:
All valid X font names, including those listed by xlsfonts(1), are available.
MS Windows:
system ansi device
systemfixed ansifixed oemfixed
Macintosh:
system application
COMPATIBILITY WITH PREVIOUS VERSIONS
In prior versions of perl/Tk the $widget->Font method was a perl wrapper on the original
"[4] X-font names (XLFD)" style as described above (which was the only form supported by
versions of core tk prior to version tk8.0). This module is provided in its original form
(it has just been renamed) via:
use Tk::X11Font;
I<$widget>-E<gt>B<X11Font>(...)
However the methods of the old scheme have been mimiced as closely as possible with the
new scheme. It is intended that code should work without modification, except for the case
of using :
@names = $font->Name;
i.e. the Name method in an array/list context. This now returns one element on all
platforms (as it did on Win32), while previously on X systems it returned a list of fonts
that matched an under-specified pattern.
Briefly the methods supported for compatibility are as follows:
$newfont = $font->Clone(-option=>value, ...>?)
Returns a new font object $newfont related to the original $font by changing the
values of the specified -options.
$font->Family - maps to -family
$font->Weight - maps to -weight
$font->Slant - maps to -slant
$font->Pixel and Point - map to -size
New code should use $font->configure to achieve same effect as last four items above.
Foundry, Swidth, Adstyle, Xres, Yres, Space, Avgwidth, Registry, Encoding
Are all ignored if set, and return '*' if queried.
$font->Name
Returns the name of a named font, or a string representation of an unnamed font. Using
$font in a scalar context does the same. Note this is distinctly different from
behaviour of X11Font's Name in a list context.
$font->Pattern
Returns a XLFD string for the font based on actual values, and some heuristics to map
Tk's forms to the "standard" X conventions.
SEE ALSO
Tk::options
Tk::X11Font
KEYWORDS
font